The Great Lakes region’s $7 billion fishery is anchored here, where more fish are spawned and caught than anywhere else in the lake system.

To the north, a similar message would be played out along the Detroit River, the St. Clair River, Lake St. Clair, and Lake Huron, up to Michigan’s Saginaw Bay.

“The entire Huron-to-Erie corridor is potentially some of the best habitat for Asian carp,” Joel Brammeier, Alliance for the Great Lakes president and chief executive officer, said. The alliance, founded in 1970, is one of the Great Lakes region’s oldest and largest environmental groups.

The Huron-to-Erie corridor has for years been among the best habitat for native fish. The native sportfishing and commercial fishing industries could collapse if Asian carp colonize that area.

That would put thousands of jobs created or supported by fishing at risk. It would likely be a blow to Great Lakes tourism, another one of the region’s economic drivers.

“That, to me, suggests we’re going to have no trouble convincing people in those parts of the lakes to understand,” Mr. Brammeier said.

The sales pitch will be different in Chicago, where carp are encroaching upon Lake Michigan via a series of Chicago-area waterways.

Henry Henderson, director of the Natural Resources Defense Council’s Midwest office, said the message for Chicago and northeast Indiana will be one of dry basements and cleaner tap water.

Mr. Henderson, an attorney who served as Chicago’s first environmental commissioner earlier in his career, said support from the Windy City will come if the project’s sold as a forward-thinking way of better managing water in the nation’s third largest city and its surrounding areas.

Chicago and northeast Indiana have been prone to flooding for years, he said. Separating the watersheds offers an opportunity to modernize Chicago’s water-distribution and wastewater networks, Mr. Henderson said.

The U.S. Army Corps of Engineers, in a 232-page report to Congress on Monday, listed a complete hydrological separation of the two watersheds among eight options for turning away Asian carp and a dozen other would-be exotics threatening to invade the Great Lakes system through Chicago-area waterways.

One option called for the status quo, which several Great Lakes congressmen and senators have dismissed as unacceptable.

Another calls for the status quo with $68 million a year on anything from poisons to public relations.

The other six call for physical barriers or construction work ranging from $7.8 billion to $18.4 billion. In many cases, the highest-priced items aren’t the barriers themselves, but tunnels and other devices that would be needed to deliver better water and reduce flooding risk for the Chicago area.

“We have to make this more than a project with a single point or some abstract Great Lakes issue,” Mr. Henderson said. “We need to show this is not just about re-plumbing Chicago. It’s about fixing a national problem.”

Congress is more likely to support the plan if it sees benefits for other watersheds, such as the Mississippi and the Gulf of Mexico, he said.

The Chicago-area waterways were built more than 100 years ago to send sewage from that metropolitan area downstream.

Redesigning the system could bring more modern sewage treatment, help improve the water quality of the Mississippi and related streams and, to some degree, help reduce sewage that contributes to the Gulf’s dead zones, Mr. Henderson said.

It also could improve transportation into the nation’s heartland by enhancing limited shipping that occurs there now with more rail and truck transportation, he said.

The concept, though, is not embraced by the shipping industry.

Tom Allegretti, American Waterways Operators president and chief executive officer, said the tugboat, towboat, and barge industry recognize the need to fend off invasive species.

But he said a physical separation of the watersheds “is neither economically feasible nor will it be effective at eliminating all identified pathways for the spread of invasive species, including Asian carp.”

“Severing a critical part of the nation’s water transportation network is too high a price to pay for a solution that is not guaranteed to stop the spread of invasive species,” Mr. Allegretti said.

His remarks were echoed by Benjamin Brockschmidt, Illinois Chamber of Commerce federal affairs director, and Mark Biel, chairman of a Chicago-area business coalition called UnLock Our Jobs and executive director of the Chemical Industry Council of Illinois.

Several Great Lakes scientists have said a complete separation of the watersheds is the only way to cut exotics off from the lake system.

But most elected officials have not committed themselves to any one of the options submitted by the Corps.

Several issued statements similar to that of U.S. Rep. Bob Latta (R., Bowling Green), whose office released one Tuesday night which said the congressman believes it “is imperative we protect the Great Lakes region’s economy, tourism, and jobs from the threat of Asian carp.”

But Mr. Latta did not go on the record as saying if he will support or oppose a physical separation.

To Mr. Brammeier, the idea of “spending billions instead of millions” shouldn’t faze people, given the complexity of the project and what’s at stake if the problems aren’t fixed.

“When we’re talking about spending this much money, we should be talking about extracting as many benefits as possible,” he said.

Mr. Henderson said the region needs to get past the animosity that was created between Illinois and other Great Lakes states, when Illinois — with help from the Obama Administration — successfully fought off attempts by Michigan, Ohio, Pennsylvania, Minnesota, and Wisconsin to close the Chicago-area locks.

“We need to reconceive this as a huge opportunity,” Mr. Henderson said. “We need to look at it as an investment for the United States as a whole.”